A champion that gets mana from taking damage

Basically the lore is Dude gets badly injured Dude wants to live. Demon of will tests his will to live He wins and the demon saves him Now he has to decide if he wants to remain human or take advantage of the demonic powers he now controls

Unique mechanic taking damage gives will Will can be used to cast spells Spells have no Cooldown The spells can be upgraded with demonic powers or human powers Demonic powers would make them deal more damage and cost less will Human powers would give aoe healing effects but lose out on the extra damage and casting more often If you have more demonic abilities than human then you would gain more armor or magic resist and have a higher max will If you had more human abilities then you would slowly generate will passively Basically he would be versatile acting like a tank support or a bruiser type character The exact spells aren’t as important as the concept, so I havent thought of any yet I should probably say the character would be a melee juggernaut with no mobility spells Maybe some melee range cc but because he could spam spells if he took enough damage, cc would be pushing it